Catalytic effects of transition metals on oil shale pyrolysis

The decomposition of kerogen of Green River formation oil shale, impregnated with transition metals, was investigated following nonisothermal thermogravimetric techniques, in the presence of hydrogen at atmospheric pressure. Experimental data were best fit by a first-order kinetic model with respect to kerogen. The effects of ambient atmosphere and heating rate were also investigated. In the absence of metals, inert and reducing atmospheres were found not to affect kinetic parameters. The frequency factor was found to increase with heating rate at a constant activation energy. The presence of metals in the oil shale matrix and hydrogen in the retorting atmosphere did not alter the kinetic order of kerogen decomposition, but it lowered apparent activation energies and increased the rate constants. These results are discussed in terms of dissociative hydrogen adsorption on the metal crystallites and hydrogen spill over to the organic matter, resulting in hydrogenation and/or cracking reactions.